Aerial refueling tanker airplanes use aerial refueling booms for transferring fuel to various types of receiving aircraft. The present U.S. Air Force operational tanker fleet (KC-135 and KC-10) utilizes director light systems that provide direction queuing to receiver pilots after contact has been made between the refueling boom nozzle and the receiving aircraft's receptacle. Operation of the director light system is automatic in the contact mode. The director light system includes two light arrays, as shown in FIGS. 1 and 2. The two light arrays include longitudinally positioned lights that display present contact position relative to the optimum contact position. The display presents longitudinal and vertical information important to the pilot of the receiving aircraft. The reference for the presented information is the refueling aircraft. The light arrays may be operated manually by the boom operator using visual cues or by a determination of the present contact position. The present contact position is determined according to refueling boom elevation position and telescopic length sensing of the refueling boom when the refueling nozzle and the receiving aircraft's receptacle are coupled. FIGS. 1 and 2 illustrate the director light systems presently used a KC-135s and KC-10s, respectively. The light assemblies for both the KC-135 and KC-10 are positioned on the lower fuselage just forward of the wings' leading edge. The row of lights on the port side of the aircraft indicates aircraft elevation relative to optimum fueling position. The row of lights on the starboard side of the fuselage indicates refueling boom telescoping position or the aircraft's fore and aft position relative to the optimum refueling point. These systems are effective tools for generating accurate contact position information. Also, they are relatively simple light arrays which are easy for pilots to understand. This ease in understanding helps lessen the receiving pilot's task load, which is already quite large with management of complicated systems internal to the aircraft. However, this system only presents contact position information. Getting to the contact position can be half the battle for receiving aircraft pilots, especially, if that pilot is greatly fatigued or stressed as a result of a difficult sortie, bad weather, or an emergency of some sort. Also, the boom operator does not receive adequate or any information that may allow the boom operator to direct the receiving aircraft pilot to the contact position.
An improved boom refueling light system is presented in U.S. Pat. No. 4,158,885 (hereinafter the '885 patent). The '885 patent includes an optical sensor for sensing receiving aircraft position and two light arrays on the belly of the aircraft. The two light arrays are controlled according to control information generated by the optical sensor and associated components. This system provides useful information through the light array assembly on the refueling aircraft that easily enables the receiving aircraft pilot to judge the receiving aircraft's position relative to the refueling boom. However, as shown in FIG. 1 of the '885 patent, the refueling boom can block the electro-optical sensor's line-of-sight to the retroreflector on the receiving aircraft. If the block occurs for a few seconds or more, a disconnect procedure may initiate or the system may continue presenting the last determined receiver aircraft position. In the latter case, the light arrays would therefore display the last determined receiver aircraft position information, which could be dangerously inaccurate. Also, reflectors must be mounted on thousands of receiving aircraft and optical sensor systems mounted onto the tanker aircraft fleet. This and the maintenance required could be prohibitively expensive as compared to just maintaining the old system..
Accordingly, there is a need for a light system that presents accurate and consistent receiving aircraft and receiving aircraft receiving nozzle pre-contact position information to the pilot of a receiving aircraft at all times during refueling. The approach information provided by the light system to the receiving aircraft pilot should be sufficient to allow the pilot to gradually work the receiving aircraft to a desired position for coupling with the refueling boom. The present invention is directed to providing such a refueling light system.